import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        long[] result=new long[80];
        result[0]=1;
        result[1]=1;
        for (int i = 2; i < 80; i++) {
            result[i]=result[i-1]+result[i-2];
        }
        Scanner sc=new Scanner(System.in);
        while (sc.hasNext()){
            int from= sc.nextInt();
            int to=sc.nextInt();
            long sum=0;

            for (int i = from-1; i < to; i++) {
                sum+=result[i];
            }
            System.out.println(sum);
        }
    }
}
